According to the CDC, among US men, cancer of the prostate is the most common type of cancer and the second leading cause of cancer death. Due to the diffuse nature of prostate cancer, there is a need for safe, inexpensive, and portable prostate tumor imaging, which MRI or nuclear imaging cannot satisfy. As one of the most sensitive in vivo molecular imaging modalities, fluorescence imaging has great potential to play an important role in preclinical and clinical studies. Indeed, in vivo fluorescence optical imaging extends across a wide range of applications, from cellular to organ levels. Unfortunately, in organ level applications, fluorescence imaging suffers from low resolution due to the high scattering nature of the biological tissue especially in deep tissue. Extensive effort has been spent to improve the resolution of fluorescence tomography (FT) by research groups from academia and industry in the last decade. However, approaches such as integrating FT with other anatomic imaging modalities such as MRI or CT does not perform well if the fluorescent target cannot be localized in the anatomical image. There are several techniques that attempt to modulate fluorescence signals using ultrasound to achieve higher resolution. However, low modulation efficiency and extremely low signal to noise ratio (SNR) are the two primary factors that make the implementation of these techniques difficult. Therefore, the low quantitative accuracy and resolution of fluorescence imaging remain as the main barriers for clinical translation of this powerful technique. To overcome these limitations, our main goal in this proposal is to develop an entirely new approach Temperature-modulated fluorescence tomography (TM-FT) that can provide high resolution images at depths up to 6 cm without sacrificing the exceptional sensitivity of fluorescence-based detection. There are two key components to this highly innovative approach: a) Temperature sensitive florescent molecular probes (thermo-dots) and b) High Intensity Focused Ultrasound (HIFU) based modulation of tissue temperature (only 3-50C) with high spatial resolution. The small size of the focal spot (~1mm) allows imaging the distribution of these temperature sensitive agents with not only high spatial resolution but also high quantitative accuracy. Development of this novel system will include: development and optimization of the TM-FT reconstruction algorithm, development of the TM-FT system and evaluation with phantom studies, and finally, validation with in vivo studies. This training proposal is geared toward the first in vivo feasibility studies of this nove imaging modality. The outcome of this proposal could be a radiation free, cost-effective, and portable tumor imaging system. Mice bearing orthotopic prostate cancer model will be used to test the hypothesis that TM-FT will provide quantitatively more accurate and higher resolution fluorescence images compared to a stand-alone FT system. If successful, the outcome will be the beginning of a new imaging modality.